iommu/vt-d: Avoid superfluous IOTLB tracking in lazy mode

commit f70c67a0ee1d07bcef40972ea22362500f3c1d41 upstream.

Intel IOMMU driver implements IOTLB flush queue with domain selective
or PASID selective invalidations. In this case there's no need to track
IOVA page range and sync IOTLBs, which may cause significant performance
hit.

This patch adds a check to avoid IOVA gather page and IOTLB sync for
the lazy path.

The performance difference on Sapphire Rapids 100Gb NIC is improved by
the following (as measured by iperf send):

w/o this fix~48 Gbits/s. with this fix ~54 Gbits/s

Cc: <stable@vger.kernel.org>
Fixes: 8d262b5e1b45 ("iommu: Handle freelists when using deferred flushing in iommu drivers")
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Link: https://lore.kernel.org/r/20230209175330.1783556-1-jacob.jun.pan@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 82d18eb02266ca4addbbc9385f4d323d4b12b6c1..d4b5d20bd6ddaa45ddbf3c877d15191c4959d524 100644 (file)
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4359,7 +4359,12 @@ static size_t intel_iommu_unmap(struct iommu_domain *domain,
        if (dmar_domain->max_addr == iova + size)
                dmar_domain->max_addr = iova;
 
-       iommu_iotlb_gather_add_page(domain, gather, iova, size);
+       /*
+        * We do not use page-selective IOTLB invalidation in flush queue,
+        * so there is no need to track page and sync iotlb.
+        */
+       if (!iommu_iotlb_gather_queued(gather))
+               iommu_iotlb_gather_add_page(domain, gather, iova, size);
 
        return size;
 }